1. Field of the Invention
The present invention relates to a method for sealing a container which is suitable for a clean box for transferring and reserving a variety of articles to be processed such as semiconductor wafers in a process for manufacturing a semiconductor, an electronic parts related product, an optical disc or the like and a container according to this method, particularly, a clean box.
2. Related Background Art
Recently, in a manufacturing process which requires a high level clean environment such as a semiconductor device manufacturing process or the like, a method such as a mini-environment or a local clean space where an entire factory is not kept clean but only the ambient environment is kept under a clean condition has been adopted. In brief, only the interior of the respective processing apparatus is kept clean, and the transfer and reservation of the articles to be processed between the respective processing apparatus (clean apparatus) are performed by using containers whose interior is kept clean (hereinafter referred to as clean boxes).
In general, the clean box has a substantially rectangular box body opened at one surface and a detachable lid for sealing the box body. In order to keep the interior of the box clean, a mechanism for sealing a gap between the lid and the body is provided so as to prevent dusts or the like from entering the interior from the outside. Conventionally, an elastic seal member such as an O-ring is mounted on the box body or the lid so as to surround an opening of the box body under the condition that the lid is closed, and the seal member is deformed by a mechanical means such as a latch mechanism that works between the box body and the lid to thereby obtain a seal force. However, there is a limit to the seal force that may be obtained by such a mechanism. For example, the conventional clean box used in the manufacturing process of semiconductor devices suffers from a problem that the seal would be insufficient so that the replacement condition could not be maintained for a long period in the seal system of the conventional clean box although the interior of the box is replaced by non-oxidized gas in order to prevent the natural oxidation of the semiconductor wafers received in the box in some case.
In contrast, a system for sealing a gap between the box body and the lid by a vacuum suction is disclosed in the commonly assigned Japanese Patent Application Laid-Open No. 10-321696. This system will be described in brief. FIGS. 1 and 2 show a vacuum suction type clean box having an opening at its bottom. FIG. 1 is a side elevational cross-sectional view of the clean box, and FIG. 2 is a plan view of the lid.
As shown in FIG. 1, the clean box 100 is composed of a substantially rectangular box body 101 which opens at one of the side surface (the bottom surface in the example of FIG. 1) and a lid 102 for closing the opening of the box body 101. A shelf-like carrier 103 for holding semiconductor wafers to be received in the box at an equal distance is fixed on the lid 102 in the example shown in FIG. 1. An annular groove 110 for vacuum suction is formed in a circumferential portion of a surface (upper surface), facing the box body, of the lid 102. As shown in FIG. 2, O-rings are mounted as the respective elastic seal members along the annular groove 110 inside and the outside of the annular groove 110. In the condition shown in FIG. 2 in which the lid 102 closes the opening of the clean box body 101, the inner space of the annular groove 110 is closed at its upper portion by the flange portion 101a of the box body, i.e., the suction space formed by the flange portion 101a of the box body and the annular groove 110 is vacuum sucked so that the lid 102 is sucked to the box body 101. The vacuum exhaust is performed from the back surface of the lid by a means (not shown) through the air passage 112 provided in communication with the annular groove 110.
Thus, the annular groove is evacuated so that the lid 102 is sucked to the flange portion 101a of the clean box 101 to thereby obtain tight seal.
The seal system of the lid for the clean box according to the vacuum suction is very strong and superior in seal force. However, in the above-described conventional system, since the respective seal members (O-rings) are provided for inside and outside of the annular groove, respectively for sealing the vacuum suction space of the annular groove, a rather great width is required for the seal portion. Accordingly, the flange portion 101a requires a width that is large to some extent for the box body 101. This may obstruct the reduction in size of the clean box.
Also, in manufacturing the clean box, it is necessary to machine two grooves for the seal members (O-rings) in addition to the groove for the vacuum suction. There is also a problem in that the number of the manufacture steps is large. This should be resolved.
In view of the foregoing defects, an object of the present invention is to provide a sealing method with simple machining for sealing a cover of a container such as a clean box while utilizing a vacuum suction system and making it possible to limit the sealing arrangement in a smaller area, and to provide a container, particularly, a clean box, manufactured with employing such sealing method.
According to the present invention, a container (preferably, clean box) includes a container body opened at one surface and a lid for closing the opening of the container body. An annular groove is formed in at least one of the container body and the lid so as to surround the opening. An elastic seal member is disposed within the annular groove along the whole length thereof. A cross-section in a width direction of the elastic seal member has both end portions whose dimension in a depth direction of the annular groove is relatively thick and an intermediate portion that is relatively thin. Thus, when the lid closes the opening of the container body, an annular suction space is defined along the intermediate portion of the seal member. Also, the suction space is sealed by elastic deformation of the both end portions of the seal member between the container body and the lid. Further, the container has an intake/exhaust port for evacuation/release of the suction space from the outside.
Thus, the characterized shape elastic seal member is disposed within the annular groove per se that may provide the suction space whereby the seal may be possible in the vacuum suction fashion while it is unnecessary to provide an additional groove for the seal member. Accordingly, it is possible to impart an effective seal that is high in sealability in the narrow width.
In an embodiment of the present invention, the annular suction space is divided into two spaces in the depth direction of the annular groove by the intermediate portion of the seal member, the intermediate portion of the seal member is provided with at least one through hole, and the two divided spaces are in communication with each other through the through hole. More preferably, a plurality of through holes may be formed substantially at an equal interval along the annular shape of the seal member.
There is provided a method for sealing a container according to the invention, the container comprising a container body opened at one surface and a lid for closing the opening of the container body, wherein an annular groove is formed in one of the container body and the lid so as to surround the opening, and an elastic seal member is disposed within the annular groove along the whole length thereof, a cross-section in a width direction of the elastic seal member having relatively thick end portions and a relatively thin intermediate portion in its dimension in a depth direction of the annular groove, whereby when the lid closes the opening of the container body, an annular suction space is defined along the intermediate portion of the seal member, and the suction space is sealed by elastic deformation of the both end portions the seal member between the container body and the lid. The method includes the step of sealing the container by vacuum exhausting the suction space.